The genus Earias occurs in Africa and two species E. insulana
(Boised) and E. biplaga WIK have been identified. Both species are being
commonly known as the spiny bollworm, the name being derived from the characteristic
bristles or spines which are formed on the larva. E. insulana is a very
important pest in Egypt and is therefore, also known as the Egyptian bollworm
(Ripper and George, 1965).
The mitral damage to the cotton crop by the spiny bollworm occurs in the early
stages of plant growth. As the cotton plant grows and produces flower buds and
unripe fruit, the attack of the spiny bollworm is diverted to those. In Egypt
insecticides are being used for controlling bollworms. Insecticides can provide
economical protection by killing insect pests that otherwise would cause significant
loss. Nevertheless, the extensive use of insecticides in cotton field has seriously
affected the population densities of the natural enemies (Yang
et al., 2002; Younis et al., 2007).
Moreover, the widespread application of pesticides might accelerate some cotton
pests, mostly insects and mites to develop resistance to certain pesticides
(Elzen and Hardee, 2003).
Fertilization or/and foliar nutrients sprays might be good tool to produce
a profitable cotton crop that competes with weeds and able to out-grow and overcome
the possible occurrence and problems resulted from diseases and insects damage.
Foliar spray can also correct deficiencies of certain required nutrients in
large amounts (macro-elements) and/or required in trace amounts (micro-elements)
(Treshow, 1970; El-Naggar, 1998;
Mesbah et al., 2000; El-Naggar,
Therefore, the present study was adopted to evaluate certain treatments of foliar nutrients, a plant growth promoter (Ascobin®), a bio-insecticide (Radiant®) (spinetoram), an insect growth inhibitor (methoxyfenozide or Runner®) and an organophosphorous insecticide (Chlorpyrifos) in different sequences to minimize E. insulana injury to and to study their probable side effect on larval protease enzyme activity and cotton yield.
MATERIALS AND METHODS
Field experiments were carried out at the Experimental Farm of Regional Research Station, Plant Protection Research Institute Agriculture Research Centre, Alexandria governorate throughout two successive cotton growing seasons of 2009 and 2010. Whereas, in both seasons an area of half feddan was cultivated with cotton variety ''Giza 88'' on April 30th. The experimental design was the split one with three replicates as well as untreated check.
The experimental areas were divided into plots (0.01 feddan) (42 m2). Each plot was separated from the adjacent one by a half-meter belt to minimize the interference of spray drift from one treatment to the other. In the growing cotton seasons of 2009 and 2010, prior to sewing, the cotton seeds were dressed with the bio-fertilizer Microbin®. The divided experimental area sprayed with 6 foliar treatments in sequences beside the untreated control. The sequences included two foliar nutrients, plant growth promoter (Ascobin®), a bio-insecticide (Radiant®), an insect growth inhibitor (methoxyfenozide) and Chlorpyrifos as standard insecticide and these sequences and the rate of application of their components are shown in Table 1.
The consequent applications of each tested compound were performed at different periods, i.e., at the beginning of flowering stage, after the fifty percentage of flowering and at the beginning of fruiting stage. During the whole period of the growing season, inspections were carried out for determining the efficacy of the tested compounds on the infestation level of E. insulana, cotton yield and the larval Protease activity. Sprayings were performed using a knapsack sprayer (20 L).
Estimation of the spiny bollworm infestation: Weekly inspections were done to determine the infestation levels of the spiny bollworm. Samples of 10 green bolls/plots were taken randomly; examined bolls for each treatment were 30 green bolls represent three replicates. The weekly estimation of the bollworm infestation level was performed over ten weeks during both seasons. In each sample, bolls were examined externally before dissection and then internally. Infestation levels were based on the existence of injury symptoms regardless of the presence of the larvae.
Cotton yield: In each treatment, ripened open bolls from thirty cotton plants were collected to determine the rate of cotton yield/plant, from which, the total yield/feddan was relatively calculated.
Effect on protease enzyme activity: Alive larvae of the spiny bollworm,
E. insulana of almost same age and weight were collected from each plot
to determine protease activity. The method of determination is described by
Charney and Tomarelli (1947).
Foliar fertilizers: A-Easterna Aminofert Plus® (Liquid)(EAP) is produced by Easterna Company for Agriculture Development (Easterna, Egypt). The main components are: amino acids (10%), saccharides and (6%), nitrogen (6%), phosphorous (4%), potassium (6%), sulphur (5%), organic matter (85%), magnesium (5000 ppm), chelated ferric (1000 ppm), chelated zinc (500 ppm), chelated manganese (250 ppm), chelated copper (150 ppm) and boron (100 ppm).
B-Greenzit SP100® is produced by Ciba Geigy limited (Basal, Swiss) and the main components are: EDTA Na2Mn (40%) and EDTA Na2Zn (43%) supplemented by Ca: 0.054, Fe: 5.40, Mo: 0.027, Mg: 0.54, Ni: 0.005, Mn: 5.54, Cu: 0.005 and Zn: 70.27 g kg-1.
Plant growth promoter: Ascobin® is produced by General Organization Agricultural Economic Fund (G.O.A.E.F) (Egyptian Ministry of Agric.). The main components are ascorbic acid+citric acid (38 %) and organic matters (62 %).
The agrochemical pesticides A-spinetoram (Radiant® 12 SC): It is a semi synthetic compound is the second generation of spinosyns group. It is a trademark of Dow Agro Sciences Co. (Dow, England).
Insect growth inhibitor (IGI): Methoxyfenozide or Runner® 24% (SC); N-tert-butyl-N-(3,5- dimethylbenzoyl)-3-methoxy-2-methyl benzohydrazide. It was supplied by Rohm and Hass Co. (Dow, England).
Organophosphorous compound: Chlorpyrifos was used as Dursban® 48% (EC); 0, 0 diethyl 0-3, 5, 6 trichloro-2-pyridyl phosphorothioate (Dow, England).
The tested foliars as applied in different sequences (fine) compared with Chlorpyrifos
as a standard insecticide and their rates of application are presented in Table
1. Data were subjected to the analysis of variance test (ANOVA), with mean
separation at 5% levels of significance, Computer program COSTAT and Duncans
Multiple Rang Test was used to compare the averages according to the method
of Snedecor and Cochran (1967).
|| The tested foliars and their rates of application during
the growing seasons of 2009 and 2010
|EAP: Easterna Aminofert Plus®
RESULT AND DISCUSSION
Estimation of the spiny bollworm infestation
Efficacy of the applied foliar treatments on the spiny bollworm infestation
during season of 2009: As illustrated results in Table 2
the level of the spiny bollworm infestation is expressed as the mean numbers
of detected spiny bollworm larvae/10 bolls. The tested foliar treatments sequences
(EAP/Greenzit S.P100/Chlorpyrifos, EAP/Radiant/Methoxyfenozide®
and Radiant/methoxyfenozide®/Chlorpyrifos) decreased efficiently
the spiny bollworm infestation to 0.44, 0.40 and 0.44 larvae/10 bolls, respectively
while, the other tested foliar sequences, resulted in a higher infestation were
obtained ranged from 0.62-0.77 larvae/10 bolls when it compared with the untreated
check (1.81 larvae/10 bolls).
Efficacy of the applied foliar treatments on the spiny bollworm infestation during season of 2010: From data in Table 2, it could be noticed that the treatment of Radiant/methoxyfenozide®/Chlorpyrifos was highly efficient and gave the lowest level of spiny bollworm infestation not exceeding 0.48 larvae/10 bolls, when it compared with the untreated check (2.74 larvae/10 bolls), This was followed by the sequence of EAP/Radiant/Methoxyfenozide® (0.92 larvae/10 bolls). Although, the other applied foliar treatments gave somewhat higher infestation levels by spiny bollworm but it was less than the untreated check and ranged from 1.40 to 1.96 larvae/10 bolls.
Obtained results of the present work are in agreement with Amin
and Gergis (2006), who found that the treatments of Agerin, Trichogramma,
Cascade, Consult, Mimic, Spinosad and conventional insecticides reduced the
infestation of the three tested pests (leaf worm , spiny bollworm and pink bollworm).
Abdel-Rhman (2004) found that the highest reduction
in the cotton bollworm infestation were induced by the use of Chlorpyrifos,
Tracer® (Spinosad) and Methoxyfenozide ®. Moreover,
El-Naggar (2003) and Mesbah et
al. (2004) illustrated that the application of Baythroid®
with Greenzit S.P100 have also lowered spiny bollworms infestation.
Also, the obtained results by Purohit and Deshpande (1994),
Mesbah et al. (2000) and El-Naggar
(2009) were in full agreements with the present aforementioned and illustrated
||The mean numbers of spiny bollworm larvae/10 bolls as affected
by the tested foliar treatments throughout the growing seasons of 2009 and
|| Effect of the tested foliar treatments on the cotton yields
(Kent./feddan) in the growing seasons of 2009 and 2010
|*A kentar (kent.) of seed cotton = 157.5 kg, **Expressed
as % of increase than the untreated check, according to Hussin
et al. (2002)
Effects on cotton yield
Efficacy of the applied foliar treatments on cotton
yield during season of 2009: The exhibited results in Table
3 indicated that the application of EAP/Radiant/methoxyfenozide®
and EAP./Greenzit ®S.P100/Radiant®
gave the highest cotton yield increase than untreated check (276.47 and 264.70%,
respectively) followed by the sequence of Radiant®/methoxyfenozide®/Chlorpyrifos
(223.52 %). On the other hand, the other tested foliar sequences gave increase
in the cotton yield ranged from 82.35% in case of EAP/Greenzit ®S.P100/Ascobin
®and EAP./Greenzit® S.P100/chlorpyrifos
to 194.11% in case of Chlorpyrifos.
Efficacy of the applied foliar treatments on cotton yield during season of 2010: As showed in Table 3 the performance of EAP/Radiant®/Methoxyfenozide® and Radiant®/Methoxyfenozide®/ Chlorpyrifos registered the cotton yield increase (900 and 800 %) followed by the treatment of EAP/Greenzit® S.P100/Radiant® (450%). Versus, the applied foliar sequences of EAP/Greenzit® S.P100/Chlorpyrifos gave the lowest increase (50%). For the other applied foliar treatments, the estimated increase of cotton yield was more or less extent, lowered but still higher than the untreated control and amounted to 100 and 150% for Chlorpyrifos and EAP/Greenzit® S.P100/Ascobin®, respectively.
The present results are in agreement with those of El-Naggar
(2003) and Mesbah et al. (2004), who concluded
that the application of bi-and/or tri-sequent sprays of the Baythroid®
with Greenzit S.P100, Greenzit N.P.K and Polymex/Ascorbic acid increased
the yield of treated cotton plants. Abdel-Rhman (2004)
stated that the treatments of Tracer® (Spinosad), Chlorpyrifos
and Methoxyfenozide ® increased the cotton yield. El-Naggar
(2009) reported that the application of Easterna followed by Super Biovert
and Spinosad in respect increased the cotton yield compared to the untreated
control in both seasons of 2006 and 2007. Meanwhile, he found that sprays of
Easterna/Greenzit S.P100/Spinosad only increased cotton yield in
season 2007. Similar results were also explained by Sun
and Xu (1986), El-Naggar (1998), Mesbah
et al. (2000) and El-Naggar et al. (2008).
Effect on the activity of larval protease on the spiny bollworm: As
indicated in Table 4 the tested foliar fertilizers and all
alternative chemical compounds had severed effects on the activity of larval
protease on the spiny bollworm, E. insulana in comparison to untreated
check. The detected differences in enzyme activity occurred after larval exposure
to the applied sequences of these compounds.
|| Effects of foliar sprays on the activity of larval protease
of Earias insulana
In this respect, the foliar treatments of Chlorpyrifos and EAP/Radiant®/Methoxyfenozide®
gave the highest value of enzyme activity which amounted to 0.697 and 0.672
OD/mg protein/min, respectively, followed by the treatment of EAP/Greenzit®S.P100/Radiant®
(0.567 OD/mg protein/min) compared to untreated check (0.194 OD/mg protein/min).
On the contrary, the treatments of Radiant/Methoxyfenozide®/Chlorpyrifos
decrease the enzyme activity to the lowest value (0.283 OD/mg protein/min).
On the other hand, the other applied foliar treatments gave somewhat higher
enzyme activity than the untreated check and ranged from 0.369 in case of EAP/Greenzit®
S.P100/Ascobin® to 0.482 larvae/10 bolls in case of
It could be concluded that the results of the present investigation indicated that the foliar treatments of EAP/Radiant®/ methoxyfenozide® and Radiant®/methoxyfenozide®/Chlorpyrifos gave the highest value and lowest value of Protease enzyme activity, respectively but in the same time, these treatments gave the same highly efficient on the spiny bollworm infestation and gave higher increase cotton yield.